1. Field of the Invention
The present invention is directed to an apparatus and method to treat or condition natural gas for use as fuel gas for a compressor.
2. Prior Art
Natural gas is ordinarily gathered from subterranean wells and delivered through pipelines where it may be further treated and then distributed.
At the early stages of the life of a natural gas well, reservoir downhole pressure forces natural gas through the tubing or piping in the well and up to the surface. As a natural gas well begins to age, the reservoir or downhole pressure will tend to decline over time. In some cases, it will eventually reach the same pressure as the pressure within the gas pipeline. At this point, the natural gas well will no longer flow on its own.
A number of solutions to this problem have been devised. One solution is a compressor which is installed on the well, typically at the surface. The compressor will act to boost the gas pressure and allow the gas to continue to flow into the pipeline. It also reduces the pressure that the well has to produce against. In other words, the compressor draws gas out of the well and discharges it into the pipeline at a high enough pressure to keep the fluid flowing.
At least two different kinds of compressors exist. A reciprocating compressor uses an internal combustion engine to drive a shaft and pistons which compress gas. A helical screw compressor uses an internal combustion engine to rotate a helical rotor which turns within a stator to compress gas.
Both kinds of compressors also often include pneumatic controls and instrumentation which use natural gas from the system to operate.
The internal combustion engine of the compressor requires fuel gas to operate. Since the compressor is often at a remote location, this fuel gas is often taken from the natural gas stream from the discharge side of the compressor. The discharge is the outlet or elevated pressure side. The pressure is generally too low on the inlet side for the gas to be utilized by the compressor fuel and control system. The discharge side gas is typically warm since compressing the gas also raises its temperature and it is saturated with water vapor and heavy hydrocarbon vapor. In cold weather, these vapors tend to condense and form liquids in the fuel lines and in the control system lines. In the event that the vapors turn into liquids (or solids when subjected to freezing temperatures), the operation of the various controls and instrumentation, as well as the compressor itself, may be interrupted.
It would, therefore, be desirable to provide a conditioner apparatus and method to condition a portion of compressed natural gas to use as fuel gas to a compressor.